1. Field of the Invention
The present invention relates to a keyswitch key apparatus used in a computer keyboard, and particularly to a keyswitch which can prevent deadlock upon depression thereon.
2. The Prior Art
Keyboards are the most popular input devices. Each key of a conventional keyboard generally has a cap connected to a column which is surrounded by a spring thus the column can contact a base thereunder upon depression of the key. The key will return to its original position after the depression force is removed. Therefore, the key has a top-down reciprocal movement during continuous clicks. However, the column has to be moved downward at least a specific depth into the base for preventing a deadlock from occurring.
Due to the trend of increasingly compact size and portable features of the electronic markets, the above top-down structure for keys used with desk top computers can not meet the requirements of a note book computer. Therefore, a leveling mechanism as disclosed in U.S. Pat. No. 4,433,225 comprising a pair of lever arms joined at intermediate portions thereof by a pivot to form a scissors-like linkage linked to a cantilevered portion included in and fixed in a keycap is provided for replacing the conventional keycap leveling mechanism. However, a keycap block is additionally mounted in the cantilevered portion by conventional heat-staking techniques, which has two slots at two ends thereof for respectively receiving and allowing studs to extend from the two scissors-like linkage arms. However, in practice, the keycap will have a lateral displacement when it is depressed downward to substantially a half pitch of a full depression pitch. Therefore the operation of the key will cause errors due to the unwanted lateral displacement thereof. U.S. Pat. No. 5,278,371 discloses different structures for keyswitches, yet the keycaps thereof may also move laterally upon depression.
U.S. Pat. No. 5,457,297 discloses a computer keyboard key switch which includes a bottom support board, a membrane circuit supported on the support board, a key base having a rubber cone and supported on the membrane circuit, a bridging device supporting board supported on the key base, a key cap, and a bridging device connected between the key cap and the bridge device supporting board and consisting of two rectangular open frames pivotally connected in a cross arrangement for permitting the key cap to be depressed to compress the rubber cone causing it to trigger the membrane circuit. However, the assembly of the crossed, pivotal frames with the key cap and the bottom support board requires two alignments which is laborious and time inefficient.
U.S. Pat. Nos. 5,382,762 and 5,466,901 introduce spring devices connected to respective lower ends of the links which are pivotally engaged to function as a scissors-like leveling mechanism in order to provide a buffering effect to stabilize the keycap during depression. However, the structure is overly complicated requiring additional registering procedures thus complicating assembly.
Therefore, it is requisite to provide an improved and simplified structure of a keyswitch key which can prevent the keycap from deadlocking during depression.